Selection of effective remediation strategies for previously oxidized mine-tailings impoundments requires an understanding of the extent of oxidation and future potential for acid generation and acid neutralization. These efforts also require quantification of the masses of secondary phases in the wastes, and potential for these phases to dissolve as the wastes continue to weather and under different remediation scenarios. For example, sulfide oxidation reactions may be well-advanced, indicating that an O<sub>2</sub>-limiting cover would no longer provide significant benefit. Similarly, soluble secondary solids produced through sulfide-oxidation reactions may accumulate within tailings pore spaces. Remediation approaches that enhance dissolution of these products have the potential to promote contaminant release. Detailed field characterization studies, and supporting laboratory studies, are required to guide decision-making. For example, results from the standard humidity test cell (HTC) method that promotes accelerated weathering reactions by exposing fresh mine tailings to a series of drying and wetting cycles can provide guidance for design of tailings disposal facilities. Modified HTC methods, which promote the effects of continued weathering of oxidized tailings can be used to guide remediation strategies. Test methods that limit the ingress of oxygen and expose fresh tailings to acidic solutions, can be used to determine acid neutralization processes. In addition, a variety of other test methods have been designed to evaluate the potential for release of accumulated precipitates through either direct dissolution or reductive dissolution processes. The results of these test methods can be integrated to guide remediation strategies for legacy mine sites.<br/>

Geochemical and mineralogical characterization of legacy mine tailings to develop remediation strategies

2019 Spring National Meeting

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